This invention relates to test systems, and more particularly to PC-motherboard-based memory-module testers.
Electronic systems such as personal computers (PCs) use DRAM memory chips mounted on small, removable memory modules. Older single-inline memory modules (SIMMs) have been replaced with dual-inline memory modules (DIMMs), 184-pin RIMMs (Rambus inline memory modules) and 184-pin DDR (double data rate) DIMMs. New kinds of memory modules continue to be introduced.
The memory-module industry is quite cost sensitive. Testing costs are significant, especially for higher-density modules. Specialized, high-speed electronic test equipment is expensive, and the greater number of memory cells on high-speed memory modules increases the time spent on the tester, increasing test costs.
Rather than use an expensive general-purpose I.C. tester, inexpensive testers based on PC motherboards have been developed. These motherboard-based testers cost only about $10K yet can replace a quarter-million-dollar I.C. tester when testing memory modules. The memory module to be tested is inserted into a test socket on a test adapter board (daughter card) mounted on the back-side of the motherboard. See “Connector Assembly for Testing Memory Modules from the Solder-Side of a PC Motherboard with Forced Hot Air”, U.S. Ser. No. 09/702,017, now U.S. Pat. No. 6,357,023.
FIG. 1 highlights testing a memory module using a horizontally-mounted motherboard. A conventional PC motherboard is mounted horizontally, but upside-down, within chassis 60. Rather than connect motherboard substrate 30 directly to chassis 60, as in a conventional PC, motherboard substrate 30 is mounted to metal plate 64 by standoffs or spacers 61. Motherboard substrate 30 is not mounted directly to chassis 60 in this embodiment, although it could be in some embodiments. Screws, bolts, or clamps (not shown) can be used to secure metal plate 64 to chassis 60.
Test adapter board 50 is mounted to well 66, while well 66 is mounted to metal plate 64. Test socket 51 is mounted to test adapter board 50, while pins 52 provide electrical connection from test socket 51 to motherboard substrate 30. The memory module 18 being tested is inserted into test socket 51. Test adaptor board 50 provides electrical connection from the module-under-test (MUT) in the SIMM/DIMM test socket 51 to the leads for the removed SIMM socket on the PC motherboard.
Motherboard substrate 30 has components 42, 44 (I.C. chips, sockets, capacitors, etc.) mounted on component-side 32 of substrate 30. Memory modules 36 are SIMM or DIMM modules that fit into SIMM/DIMM sockets 38. SIMM/DIMM sockets 38 (hereinafter DIMM sockets 38) have metal pins that fit through holes in substrate 30. Expansion cards 46 are plugged into expansion sockets that are also mounted onto component-side 32 of substrate 30. Cables 48 and expansion cards 46 are bulky but do not interfere with a robotic arm inserting memory module 18 into test socket 51 since cables 48 and expansion cards 46 are mounted below substrate 30, while test socket 51 is mounted above substrate 30. Cables 48 and expansion cards 46 are kept out of the way inside chassis 60.
Test adapter board 50 is a small circuit board that allows an automated handler, a person, or a robotic arm easy access to SIMM/DIMM test socket 51 that is mounted on test adaptor board 50. Test socket 51 on one surface of test adapter board 50 mates with connectors on SIMM/DIMM memory module 18, the module-under test. The other surface of adaptor board 50 has adapter pins 52 inserted in holes to make electrical contact. These adaptor pins are soldered into through-holes in adaptor board 50 and in substrate 30. Adapter pins 52 are arranged to have the same arrangement and spacing as the substrate-mounting pins for DIMM sockets 38. One or more of DIMM sockets 38 has been removed from the component side of the PC motherboard, leaving the through-holes. Adapter pins 52 are then fitted through the exposed through holes for the removed SIMM socket. Rather than push the pins through from component-side 32, adapter pins 52 are pushed through from solder-side 34 to component-side 32.
Top plate 75 can be mounted to chassis 60 in a variety of ways, such as by standoffs or metal guides or brackets. Top plate 75 has an opening to allow access to test socket 51 so that a robotic arm can insert and remove memory module 18 from test socket 51. Heated air may be blown between top plate 75 and metal plate 64, past memory module 18. Cooling fan 71 is provided in chassis 60 to cool motherboard substrate 30 and its components 42, 44 and expansion cards 46.
A larger chassis with multiple openings on the top, each for holding a metal plate 64 with a horizontally-mounted motherboard and test adapter board can be used. This allows for parallel testing using several motherboards and test sockets.
FIG. 2 is an overhead diagram looking down on a multi-motherboard test station with overhead rails for an x-y-z robotic handler. See Co et al., Automated Multi-PC-Motherboard Memory-Module Test System with Robotic Handler and In-Transit Visual Inspection, U.S. Pat. No. 6,415,397. Operator 100 can sit in front of the test station, controlling operation with a touch-screen or keyboard. Trays of untested memory modules can include a barcode that is scanned in to main system interface 65 by operator 100 before the tray is put into input stacker 63. Robotic handler 80 then picks untested modules that are moved over to input tray 62 by stacker 63. The modules are first inserted into leakage tester 82. Passing modules are then moved by robotic handler 80 to the test socket on the test adaptor board on the solder-side of one of motherboard substrates 30 for testing.
Modules that fail the motherboard or leakage test are placed on repair tray 76 by robotic handler 80. Modules passing the motherboard test are pulled from the test socket by robotic handler 80 and moved in front of cameras 75 for visual inspection. Modules failing visual inspection are dropped into VI tray 78. Passing modules are placed on output tray 72 and full trays are moved by stacker 73 to the front of the test station where operator 100 can remove them.
Each of the motherboards is mounted horizontally and upside-down and fits into a well in the frame of the test station. The test station has a surface at about bench-top level composed of the exposed solder sides of the motherboards in the wells in the frame. Robotic handler 80 rides on rails 92, 94 mounted above the level of the motherboards, such as above the head of a seated operator 100. Operator 100 also replaces repair tray 76 and VI tray 78 with empty trays when full.
Fixed rails 92, 94 in the x direction allow movable y-rail 96 to travel in the x direction. Robot arm assembly 98 then travels in the y direction along y-rail 96 until robot arm assembly 98 is directly over the desired position, such as a test socket on an adaptor board, or an input or output tray. An elevator arm on robot arm assembly 98 then moves up and down, pulling out (up) a module or inserting a module into (down) a test socket or tray. Robot arm assembly 98 can also rotate or spin the module into the desired position.
FIG. 3 is a diagram of a multi-motherboard test system with horizontally-mounted motherboards. Each motherboard substrate 30 is mounted horizontally, parallel to the bench top, but has its solder-side facing up, hiding the expansion cards, cables, and components underneath the test-station frame. Each motherboard has a test adaptor board 50 mounted on the solder-side of substrate 30. Each test adaptor board has at least one test socket that can receive a memory module that is inserted by robotic handler 80.
The horizontal mounting of the motherboards limits the number of motherboards that can be fitted in the test station, since each motherboard requires an area of at least its length by its width, plus spacing between adjacent motherboards. A total of just 10 motherboards are fitted into the frame of the test station in this example.
What is desired is a multiple-motherboard robotic test system with a higher density of motherboards and test sockets. A higher-density test system that can test more memory modules by more tightly packing motherboards into the test system is desirable.